A protection relay is a microcontroller based intelligent electronic device with a basic function to protect electrical equipment by tripping a circuit breaker and interrupting a power line in case of over current or earth fault situations. The tripping signal on behalf of a trip coil or other actuator of the circuit breaker is generated by the protection relay when, for example, the measured current in the line exceeds a nominal or preset value for a predefined time period. In certain situations such as Ring Main Units (RMU) installations in urban areas, a self-supplied relay may be used. The self-supplied protection relay utilizes energy from the current sensing transformers to supply to the relay electronics circuit and the energy to operate trip coils. A self-supplied relay may be customized by an user through mechanical binary or Dual In-line Package (DIP) switches for parameter setting, or alternatively through battery-power alphanumeric LCD based Human Machine Interfaces (HMI). The HMI may be a detachable component as disclosed in the WIPO publication WO2009071454.
The dip switches based HMI can have limited functionality (e.g., restricted to binary combinations achievable for given dip positions), apart from the constraints that a user has to do for decoding the switch position through a table to understand the interpretation of switch positions with respect to functionality being configured. An HMI such as using push buttons or touch screen interface enhances the primary function of the product through an interactive user interface by displaying the various parameters of the relay including the line current measurements, protection settings, Event logs, etc. Such HMI can also facilitate fine tuning of the achievable settings through given DIP combinations.
In case of a self powered relay, the following parameters as an example may be set with the help of DIP switches settings:
1. Nominal Current Is
2. Low set over current & earth fault protection stage
                i. Setting range of pickup current ‘I>’, ‘Io>’        ii. Setting range of definite time delay ‘t>’, ‘to>’        iii. Setting of inverse time characteristics ‘CI’, ‘CE’        iv. Setting range of time multiplier ‘K’, ‘Ko’3. High set phase over current & earth fault protection stage        i. Setting range of pickup current ‘I>>’, ‘Io>>’        ii. Setting range of definite time delay ‘t>>’, ‘to>>’4. Earth fault measurement: Internal/External5. HMI: Enabled/Disabled        
The HMI provides fine settings to setting done by DIP. For example by DIP t> is set to 0.05 & next possible setting by DIP is 0.07. In this case with the help of HMI t> can be set to 0.06 by applying fine setting value of 0.01.
In relays, the DIP positions can, for example, only be used internally for further processing. In self powered relays mechanical switches like a DIP or resistive potentiometers have been used to permit the settings of relay even in unpowered condition, in the most easiest and cost effective way. The settings and changes done by DIP are sensed by relay & then used internally for further processing. In this whole process normally there is no feedback to user, that whether changes are sensed properly or not. Further, DIPs are mechanical switches, which can be prone to changes in case of both powered and unpowered situation. So there are possibilities of tampering of settings when the relay is OFF. Therefore, it would be desirable to have feedback on the DIP switch settings and any change made in the setting in the powered and unpowered situation.